Multimode semiconductor lasers for adaptive self-mixing sensors

Self-mixing or optical feedback interferometry sensors have been demonstrated as compact and versatile non-contact optical sensor for various applications. One issue, though, appears when the level of optical feedback is strong. When that occurs, detected signals are perturbed and critical information is lost. Current solutions to this problem add extra optical component, which makes the set-up more complex. We present a technique, based on multimode semiconductor lasers and a feedback control loop, that adjusts the laser regime (single mode or bi-mode) based on the estimated level of optical feedback without adding extra optical devices, therefore keeping the simplicity of self-mixing sensors. Experimental results demonstrate that no information is lost even when the feedback is strong.